/*
FUNCTION
        <<memcpy>>---copy memory regions

ANSI_SYNOPSIS
        #include <string.h>
        void* memcpy(void *restrict <[out]>, const void *restrict <[in]>,
                     size_t <[n]>);

TRAD_SYNOPSIS
        #include <string.h>
        void *memcpy(<[out]>, <[in]>, <[n]>
        void *<[out]>;
        void *<[in]>;
        size_t <[n]>;

DESCRIPTION
        This function copies <[n]> bytes from the memory region
        pointed to by <[in]> to the memory region pointed to by
        <[out]>.

        If the regions overlap, the behavior is undefined.

RETURNS
        <<memcpy>> returns a pointer to the first byte of the <[out]>
        region.

PORTABILITY
<<memcpy>> is ANSI C.

<<memcpy>> requires no supporting OS subroutines.

QUICKREF
        memcpy ansi pure
	*/

#include <section_config.h>
#include <basic_types.h>
#if defined ( __GNUC__ )
#include <_ansi.h>
#endif
#include <string.h>

/* Nonzero if either X or Y is not aligned on a "long" boundary.  */
#define UNALIGNED(X, Y) \
  (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))

/* How many bytes are copied each iteration of the 4X unrolled loop.  */
#define BIGBLOCKSIZE    (sizeof (long) << 2)

/* How many bytes are copied each iteration of the word copy loop.  */
#define LITTLEBLOCKSIZE (sizeof (long))

/* Threshhold for punting to the byte copier.  */
#define TOO_SMALL(LEN)  ((LEN) < BIGBLOCKSIZE)

LIBC_ROM_TEXT_SECTION
_LONG_CALL_
void *_memcpy(void *__restrict dst0, const void *__restrict src0, size_t len0)
{
#if defined(PREFER_SIZE_OVER_SPEED)
	char *dst = (char *) dst0;
	char *src = (char *) src0;

	void *save = dst0;

	while (len0--) {
		*dst++ = *src++;
	}

	return save;
#else
	char *dst = dst0;
	const char *src = src0;
	long *aligned_dst;
	const long *aligned_src;

	/* If the size is small, or either SRC or DST is unaligned,
	   then punt into the byte copy loop.  This should be rare.  */
	if (!TOO_SMALL(len0) && !UNALIGNED(src, dst)) {
		aligned_dst = (long *)dst;
		aligned_src = (long *)src;

		/* Copy 4X long words at a time if possible.  */
		while (len0 >= BIGBLOCKSIZE) {
			*aligned_dst++ = *aligned_src++;
			*aligned_dst++ = *aligned_src++;
			*aligned_dst++ = *aligned_src++;
			*aligned_dst++ = *aligned_src++;
			len0 -= BIGBLOCKSIZE;
		}

		/* Copy one long word at a time if possible.  */
		while (len0 >= LITTLEBLOCKSIZE) {
			*aligned_dst++ = *aligned_src++;
			len0 -= LITTLEBLOCKSIZE;
		}

		/* Pick up any residual with a byte copier.  */
		dst = (char *)aligned_dst;
		src = (char *)aligned_src;
	}

	while (len0--) {
		*dst++ = *src++;
	}

	return dst0;
#endif /* not PREFER_SIZE_OVER_SPEED */
}
